Fuel injector having self-cleaning filter

ABSTRACT

A precision fuel injector having an inwardly opening pressure operated valve positioned in a bore forming a valve chamber and guided for reciprocal movement to open and close the valve wherein the valve guide at the end of the valve chamber opposite the valve tip is provided with a sleeve extending into the valve chamber to provide an integral filter. The sleeve is interposed between the fuel inlet and the valve chamber and provides communication therebetween through a pair of annular clearances having a width which is one-half or less of the diameter of the discharge orifices of the injector to trap solid particles and prevent the blockage thereof. The filter construction retains the trapped particles in the flow path where the velocity of fuel flow is maximum to subject them to the repetitive high pressure hydraulic forces as sequential measured charges of fuel are delivered to the injector to hammer them against the hardened metal edge of the filter and pulverize them to render the filter self-cleaning.

Davis et a1.

[ FUEL INJECTOR HAVING SELF-CLEANING .FILTER [75] Inventors: Charles W. Davis, Simsbury; Vernon D. Roosa, West Hartford, both of Conn.

[73] Assignee: Stanadyne, Inc., Hartford, Conn.

by said Davis 22 Filed: Nov. 29, 1972 [21] Appl. No.: 310,269

[52] US. Cl. 239/86, 239/533 [51] Int. Cl. F02m 55/00 [58] Field of Search; 239/86, 533; 138/43 [56] References Cited 9 UNITED STATES PATENTS 1,633,320 6/1927 Franchetti 239/86 1,990,875 2/1935 Mock 239/86 2,067,131 1/1937 Schlaupitz 239/86 3,499,605 3/1970 Dreisin 239/86 Primary Examiner-M. Henson Wood, Jr.

Assistant ExaminerMichael Y. Mar

Attorney, Agent, or Firm-Prutzman, Hayes, Kalb & Chilton Aug. 13, 1974 [57] ABSTRACT A precision fuel injector having an inwardly opening pressure operated valve positioned in a bore forming a valve chamber and guided for reciprocal movement to open and close the valve wherein the valve guide at the end of the valve chamber opposite the valve tip is provided with a sleeve extending into the valve chamber to provide an integral filter. The sleeve is interposed between the fuel inlet and the valve chamber and provides communication therebetween through a pair of annular clearances having a width which is one-half or less of the diameter of the discharge orifices of the injector to trap solid particles and prevent the blockage thereof. The filter construction retains the trapped particles in the'flow path where the velocity of fuel flow is maximum to subject them to the repetitive high pressure hydraulic forces'as sequential measured charges of fuel are delivered to the injector to hammer them against the hardened metal edge of the filter and pulverize them to render the filter selfcleaning.

2 Claims, 2 Drawing Figures FUEL INJECTOR HAVING SELF-CLEANING FILTER This invention relates to fuel injectors for internal combustion engines.

Fuel injectors of the type contemplated by this invention have a plunger or valve which is lifted from its seat by the pressure of fuel delivered to the injector by an associated high pressure pump in measured charges in timed relation with the associated engine.

It is an object of this invention to provide an improved injector incorporating an internal filter. Included in this object is the provision of such a filter which is substantially self-cleaning.

Another object of this invention is to provide an improved injector incorporating means for pulverizing solid particulate matter contained in the fuel delivered to the injector.

Other objects will be in part obvious and in part pointed out more in detail hereinafter.

The invention accordingly consists in the features of construction, combination of elements and arrangement of parts which is exemplified in the construction hereafter set forth, and the scope of the invention is indicated in the appended claims.

In the drawing:

FIG. 1 is a fragmentary cross-sectional view of a fuel injector embodying the present invention; and

FIG. 2 is an enlarged fragmentary cross-sectional view showing the valve guide of FIG. 1.

The exemplary injector shown in the drawing and embodying the present invention is of the pressureoperable type and includes an elongated tubular body having a discharge tip 12 rigidly positioned at one end thereof. The tubular body 10 further provides a central longitudinal bore extending throughout its length to form a valve chamber 14. Located within the valve chamber 14 is a rod-like plunger or valve 16 having a conical tip 18 which cooperatively engages a valve seat 20 to control the discharge of fuel from the valve chamber 14 through discharge orifices 22. An annular valve guide generally indicated at 24 is positioned I blockage of the nozzle or damage to the valve tip or within the bore of the tubular body 10 at one end of the valve chamber 14 to slidably mount and align the valve 16 with the valve seat 20 for rapid reciprocal movement under the influence of fuel pressure within the bore 14 acting against the bias of spring 26. The injector is provided with a fuel inlet 28 communicating with the valve chamber 14 for the delivery of discrete charges of high pressure fuel to the bore 14 from an associated pressure charge pump, not. shown.

As shown in FIG. 1, the upper end of the valve 16 engages a spring seat 30 which is in turn engaged by biasing spring 26. The other end of biasing spring 26 is similarly provided with a spring seat 32 to cause the spring to exert an axial force on the valve 16. An extension 42 of the spring seat 32 limits the lift of the valve 16 away from the valve seat 20.

In a typical injector of the type involved in this invention the hydraulic pressure within the valve chamber 14 required to open the valve against the bias of the spring 26 is of the order of 2,000 to 3,000 psi. It is apparent that the seal between the valve tip 18 and the valve seat 20 must withstand such pressures without leakage and it is essential that these surfaces not be scored or damvalve seat by entrained debris or particulate matter in the fuel delivered to the nozzle.

As shown in the drawing, the integral annular sleeve 58, which extends into the valve chamber 14 from the valve guide 24, is provided.

The sleeve 58 surrounds the valve 16 in spaced relation therewith and is interposed between the fuel inlet 28 and the valve chamber 14. The exterior of the sleeve 58 defines with the surrounding bore 60 an annulus 66 for the free flow of fuel therein. An annular ridge 62 defines with the surrounding bore 60 a narrow annular passage 64 which communicates with the valve cham ber 14. The annular passage is dimensioned, with respect to the diameter of orifices 22, so that any particle passing through passage 64 will freely pass through an orific 22. Thus passage 64 serves to prevent the passage into valve chamber 14 of any particles of a size which may block the orifices 22. In practice, the radial clearance of the passage 64 has been established at 50 percent or less of the diameter of an orifice 22. For example, where the diameter of an orifice 22 is 10 mils, the radial clearance of the passage 64 is preferably 2 mils to a maximum of 5 mils.

Since the concentricity of the sleeve 58 and the bore 60 is important in determining the maximum and minimum clearance of the passage 64, there is, in accordance with another aspect of this invention, provided a pilot 70 which engages the end of the bore 60 with a precision fit to concentrically locate the sleeve 58 within the bore 60 and assure a substantial uniformity of the passage 64.

It is apparent that an accumulation of metal chips or otherdebris in the annulus 66 would choke the passage 64 and result in an increased line pressure at inlet 28,

the same as plugging of the orifices 22. A feature of the invention is that it provides means for pulverizing chips or other debris entrained in the fuel until it is reduced to a size that will readily pass through the passage 64. The passage 64 serves as a restriction to the flow of fuel from the inlet to the valve chamber 14. As a result the velocity of flow of fuel is maximized at the inlet of the passage 64 where the chips or debris are lodged to maximize the impact and hammering of the chips against the ridge 62 which is formed of a hardened steel, thereby pulverizing the chips as the repetitive measured charges of high pressure fuel are delivered to the injector to render the filter provided by the sleeve 58 self-cleaning.

aged in use. Moreover, if the orifices 22 are blocked by solid particulate matter entrained in the fuel or other debris such as may result frombrass, aluminum, or

In order to increase the capacity of the filter afforded by the sleeve 58 there is provided, in accordance with the illustrated preferred embodiment of the invention, a second edge filter on the sleeve 58. As shown, a second annular ridge 72 is provided adjacent the annulus 66 spaced by the same annular clearance gap with the peripheral wall of the bore 60 as the annular ridge 62 to provide a parallel flow path for the fuel from the inlet 28 to the valve chamber 14. Communication is provided through this second flow path by means of an annulus 74 and radial flow passages 76 through the apertures.

From the foregoing, it will be apparent that this invention provides an injector incorporating a novel selfcleaning integral internal filter without interfering with the operation of the injector.

As will be apparent to persons skilled in the art, various modifications and adaptations of the structure above-described will become readily apparent without departure from the spirit and scope of the invention, the scope of which is defined in the appended claims.

We claim:

1. In a fuel injector, a tubular body having a valve chamber, a valve guide mounting a pressure operable valve disposed in the valve chamber and a spring biasing the valve toward a valve seat having a discharge orifice, the improvement wherein the valve guide is proery of said tubular body to provide parallel restricted passages providing communicating between said annulus and said valve chamber.

2. In a fuel injector, a tubular body having a valve chamber, a valve guide mounting a pressure operable valve disposed in the valve chamber and a spring biasing the valve toward a valve seat having a discharge orifree, the improvement wherein the valve guide is provided with a generally cylindrical sleeve extending into the valve chamber, said sleeve being interposed in the flow path of the fuel from the injector inlet to the valve chamber and defining with the inner periphery of said tubular body a restricted clearance providing communication between said inlet and said valve chamber, the width of said clearance being less than the diameter of said discharge orifice and means for maintaining the debris trapped by the filter at the entrance to said clearance where it is subjected to the maximum velocity of flow of fuel from the inlet to the valve chamber thereby to maximize the impact forces applied to the debris to pulverize the same and render the filter provided by the sleeve self-cleaning. 

1. In a fuel injector, a tubular body having a valve chamber, a valve guide mounting a pressure operable valve disposed in the valve chamber and a spring biasing the valve toward a valve seat having a discharge orifice, the improvement wherein the valve guide is provided with a generally cylindrical sleeve extending into the valve chamber, said sleeve being interposed in the flow path of the fuel from the injector inlet to the valve chamber, the outer periphery of said sleeve having a pair of spaced annular peripheral ribs separated by an annulus accommodating the free flow of fuel therein, said peripheral ribs cooperating with the inner periphery of said tubular body to provide parallel restricted passages providing communicating between said annulus and said valve chamber.
 2. In a fuel injector, a tubular body having a valve chamber, a valve guide mounting a pressure operable valve disposed in the valve chamber and a spring biasing the valve toward a valve seat having a discharge orifice, the improvement wherein the valve guide is provided with a generally cylindrical sleeve extending into the valve chamber, said sleeve being interposed in the flow path of the fuel from the injector inlet to the valve chamber and defining with the inner periphery of said tubular body a restricted clearance providing communication between said inlet and said valve chamber, the width of said clearance being less than the diameter of said discharge orifice and means for maintaining the debris trapped by the filter at the entrance to said clearance where it is subjected to the maximum velocity of flow of fuel from the inlet to the valve chamber thereby to maximize the impact forces applied to the debris to pulverize the same and render the filter provided by the sleeve self-cleaning. 